A. Field of the Invention
The present invention relates to a processing apparatus for coating the surfaces of articles to be processed such as semiconductor wafers or LCD substrates with a processing liquid such as a resist liquid, and more particularly to a resist processing apparatus having a function for removing unnecessary coated films formed on the peripheral portions of the articles. The present invention also relates to a method of performing resist processing.
B. Description of the Related Art
With a method of manufacturing semiconductor apparatuses or the like, the surfaces of articles to be processed such as semiconductor wafers are coated with a processing liquid by rotating the articles or spraying the processing liquid on the articles. In the process of this kind, the thickness of each film is uniform just after the process. However, as the time elapses, the processing liquid swells and becomes thick at the peripheral portion of each article to be processed by the surface tension, and the processing liquid extends to the peripheral portion of the undersurface of the article, thereby forming unnecessary films.
When such nonuniform resist films are formed on the peripheral portion of the processed article, they are not removed completely from the peripheral portion of the article but are left on it. During the transportation of the articles after they have been processed, the retained resist is likely to peel off, resulting in generation of particles.
In order to solve this problem, the unnecessary coated films must be removed from the peripheral portion of the article to be processed after the surface of the article has been coated with the resist liquid or the like.
An apparatus for removing unnecessary coated films from the peripheral portion of each processed article is disclosed in Japanese Examined Patent Application Publication No. 3-76777.
The removing apparatus comprises upper and lower supplying pipes of a washing liquid provided so as to face the upper surface and the undersurface of the peripheral portion of a wafer and an exhaust pipe disposed between the upper and lower supplying pipe, for collecting the used washing liquid supplied from the supplying pipes. The washing liquid is supplied from the supplying pipes to the wafer and is sucked by the exhaust pipe simultaneously. The removing apparatus forcibly exhausts all the washing liquid and dissolved substances through the exhaust pipe to prevent the washing liquid from flowing toward the center of the wafer.
However, this removing apparatus has such a structure that two supplying pipes are used to supply a washing liquid to the upper surface and the undersurface of each wafer. The washing liquid supplying systems are complicated and increase the manufacturing cost of the removing apparatus. Further, as two washing liquid supplying systems are required, the size of the removing apparatus is large. Because a great amount of washing liquid is supplied from the two washing liquid supplying systems, the running cost of the removing apparatus increases. Since the washing liquid is supplied to the upper surface and the undersurface of the peripheral portion of each wafer and the used washing liquid is collected by the exhaust pipe disposed between the supplying pipes and extending perpendicularly to them, the washing liquid is not supplied to the vertical edge of the peripheral portion of the wafer, and it is difficult to remove the unnecessary coated films completely.